Process and apparatus for the specific gravity classification of bulk substances utilizing finely granulated separating media



W. VOG EL ATUS Aug. 31, 1954 2,687

PROCESS AND APPAR FOR THE SPECIFIC GRAVITY CLASSIFICATION OF BULKSUBSTANCES UTILIZING FINELY GRANULATED SEPARATING MEDIA Ongmal FlledJuly 23, 1947 2 Sheets-Sheet l Aug. 31, 1954 w. VOGEL PROCESS ANDAPPARATUS CLASSIFICATION OF B 2,687,804 FOR THE SPECIFIC GRAVITY ULKSUBSTANCES UTILIZING FINELY GRANULATED SEPARATING MEDIA Original FiledJuly 23, 1947 2 Sheets-Sheet 2 Patented Aug. 31, 1954 PROCESS ANDAPPARATUS FOR THE SPE- CIFIC GRAVITY CLASSIFICATION OF BULK SUBSTANCESUTILIZING FINELY GRANU- LATED SEPARATING MEDIA Walter Vogel, Santiago,Chile Original application July 23, 1947, Serial No.

763,121. Divided and this" application August Claims priority,application Switzerland September 11, 1946 11 Claims. 1 I The presentinvention relates to the process and apparatus for the specific gravityclassificationof bulk substances utilizing finely granulated separatingmedia. This application is a divisional of my prior application SerialNo.

763,121gfiled July 23,1947, now patented under No. 2,612,269, datedSeptember 30, 1952, and entitled Process and Apparatus for SpecificGravity Classificationof Bulk Substances.

As indicated in'said application, the separating media may be'sand,gravelor other material reduced to suitable size inconjunction withapparatuseffective to carryout the process.

More specifically the present invention relates to a process andapparatus for specific gravity classification of bulk substances inwhich the finely granulated media in the material to be separated flowin strata in an inclined stream greater than the natural angle ofreposeof the media. and includesfthe discharge of the media and the materialafter first changing the directionof flow thereof at different relativevelocities.

More particularly the invention relates to a dryprocess for separatingsolid materials in accordance with theirspecific gr'avities' in acontinuously moving stream of finely divideddry separating mediumincluding feeding the material tobe separated andthemedium at one'end ofthe zone disposed at an angle at least greater than thematerialangle orrepose; changingthe movement of thestream from a straight line flow toan arcuate flow tangentially to the straight line now thereby impartingdifferent relativevelocities. to the strata, separating the strata inaccordance with the velocity thereof and removingthe separated materialsfrom the respective strata.

From GermanPatent740,005and a's'set forth in my above identified priorapplication, it is knownto separate in a stream of finely granulatedseparatingmedium flowing in atrough means withthevelocity ofthediiferent layers increasingfrom thejlower to the upper layers. Insuch instances the stream with separating medium flows inthe manner of aliquid in which, inaccorda'nce with the Archimedean principle, theheaver particles" gradually sink to'the bottom of theseparating meduimand. the lighter particles' are carried to thetop.With'such'arrangeinents the diirerentvelocities of the advafice movementof the finely'granulated separating medium is-"achieved by thechcice ofan gle of-slope' of the trough within which process is effected, as wellas by adjiistinent'ofthe blade orthe like which dividesthe stream'ofseparat- 2 ing medium and which blade is located at the discharge end ofthe trough. As pointed out in my prior application, such known processesdo not accomplish satisfactory separation since the different velocitiesupon which principle the process is predicated, do not remain constantthroughout the separating medium until the same reaches the dischargeend Therefore, and consistent with the statement of the invention, it isan object of the present invention to provide a process and an apparatusthat eliminates such drawbacks in the prior art in a manner diiferentfrom that embodied in my prior application Serial No. 763,121 now PatentNo. 2,612,269 and which will permit adequate separation, the intensityof which can be regulated at will since the invention, provides for thedischarge of the difierent layers of separating medium at differentvelocities.

Specifically the present invention has for an object to provide animproved process and apparatus for effecting specific gravitybulkclassification in which separating media flows through a trough slopingat an angle at least greater than the natural angle of repose and bydischarging the media in the from of a nappe so that the layers moredistant from the center of the arc traverse a greater distance in agiven period of time compared with the layers closer to the center ofthe nappe.

In the accomplishment of the invention as hereinabove set forth,increased velocity is imparted to the advance movement of the upperlayers of the separating medium. However the a present invention has foran object to provide for an inversion of this principle by increasingthe velocity of the lower layers by the provision of a conveyor troughsloping upwardly at an angle greater than the angle, of repose in whichthe rate of feed of the lower layers is greater thanthe rate of feed ofthe upper layers.

The specific gravity classification of more than two substances can veryconveniently be accomplished by means of this invention and for thispurpose two or more superimposed layers of separating media diminishingin specific gravity fromthe bottom to the top, are used simultaneously.If for example it is desired to obtain three products, two finelygranulated separating media ofdiverse specific gravity are used,thatis,an upper layer of lesser specific, gravity over a lower layer ofgreater specific gravity. These" layers advance in the troughsimultaneously. At the discharge end of the trough the light weightsubstance will be in the uppermost layer, the middle weight substancewill be in the intermediate layer, and the heavy weight substance willbe in the lowermost layer, and. same may be removed therefrom byscreening each layer individually so as to recover the separating mediafor re-use in the trough aforementioned.

It is advantageous to use separating media having similar angles ofrepose. In some cases, in order to avoid intermingling of the layers, itmay be expedient that the granulations of the separating medium ofgreater specific gravity be smaller than the granulations of theseparating medium of lesser specific gravity. It may also beadvantageous to have between the two layers of separating media ofdiverse specific gravities, an intermediate layer composed of a mixtureof the adjoining layers, which mixture generally forms spontaneouslyduring operation of the apparatus covered by this invention.

In order to maintain a constant separative in tensity, the specificgravities as well as the angles of repose of the granulates ofseparating media should be maintained without variation. For thispurpose the invention may be complemented with means for the continuouselimination of residues accumulating during the separating process, aswell as for elimination of the secondary granuiations that graduallyaccumulate in the separating media through screening thereof after thedivision of the diverse layers, which diminishes the purity thereof as aresult of the inclusion of extraneous material.

For greater convenience it is possible to pass through a cleaningdevice, a partial stream of the separating medium used in any closedcircuit. The method used may be, for example, either hydromechanicalseparation in a decantation machine, or pneumatic cleaning by means ofair currents. If the hydromechanical method is used, the cleanedseparating medium must be dried before being re-used in the separatingprocess.

Many advantages are derived by using as a separating medium a materialcapable of being magnetized, the cleaning of which may subsequently beaccomplished by magnetic separation, by merely passing a partial streamof the separating medium over an adequate magnetic field.

The purpose of this invention may also be achieved by using as aseparating medium, hollow iron balls, in sizes and wall thicknessesproportionate to the specific gravity desired. It is likewise possibleto use cast materials such as metallic alloys or glass, slag and ceramicmaterials, such as porcelain or materials held together by means ofresins or other binding agents, including ferrous aggregates, in anygiven size required, and also, if necessary, spherical in structure. Theuse of such materials is particularly applicable in the separation oflarge bulk substances, inasmuch as in such cases it is thereby possibleto select the most adequate proportion of the size of granulation of theseparating media.

Finally, advantages may be derived by selecting as a separating medium amaterial whose hardness is greater than the hardest residue of thesubstance to be separated, so that during continuous contact thereofwith the substance being separated in the trough, the residue as well asthe secondary granulations will continue to disintegrate as a result offriction with the harder separating medium, and can then be separatedtherefrom by a simple screening operation. For this purpose the size ofgranulation chosen for the separating medium must be larger than thesize of the perforation or mesh of the screen used therefor. Forexample, in the separation of stock-piled bulk coal, the separatingmedia used may be hollow cast steel or basalt balls, or solid glassballs 8 to 10 in diameter. Thus a 12 mm. mesh screen may be used torecover the substance to be separated, and an 8 mm. mesh screen may beused to recover the separating medium from the residue, and if thescreen be combined with a conveyor, it will be possible to return in acontinuous manner, the screened separating medium to the principalcircuit of the process effected by this invention.

The invention will now be described with reference to particularapparatus illustrated in the accompanying drawings, in which:

Figure l is a diagrammatic view in vertical cross-section of one form ofthe apparatus;

Figure 2 is a diagrammatic View in vertical cross-section of anotherform of the apparatus,

and

Figure 3 is a diagrammatic view partially in vertical cross sectionillustrating the form of apparatus of Figure 1 embodiedin a circuitincluding the return of the separating media to the troughs and thecleaning and drying of a partial stream thereof.

As illustrated in the drawing, the apparatus comprises a downwardlysloping covered trough i including a bottom i which trough is sloped atan angle greater than the angle of repose of the separating media. Atthe upper or head end of the trough is a feed hopper which includesfunnels 2 and 3 for receiving the separating media and between thesefunnels there is provided a duct 3 through which is introduced thesubstance to be separated. The discharge end of the trough i terminatesover roller 5 rotatably mounted on horizontal shaft 6 and driven bysuitable transmission means including motor M. The bottom i of thetrough is disposed in tangential relation with respect to the surface ofthe roller ii. The roller includes side extensions l of a height orradial distance from the center of shaft ii such that they approximatethe height of the side walls of the trough i. These side extensions imove very close, during rotation, to the side walls of the trough and asillustrated the same are partly covered by a conveyor belt 8 passingover rollers 9 and ii constituting guide rollers, one of which is drivenfrom the motor. As indicated this belt bearing on and moving with therim or periphery of the side extensions ll diverts the flow of mediumand materials passing over the rotating roller 5. The action is suchthat the flow through the space defined by the surface of the roller,the inner surface of the side extensions and the conveyor belt is suchthat the superimposed layers of separating medium furthest removed fromthe surface of the roller advances at increased velocity. As theseparating medium discharged by the belt passes over the lower pulley isit is divided into partial streams by one or more dividing blades l ifrom which partial streams the diverse fractions of the substance to beseparated are recovered individually. It is believed clearthat thesurface of the roller 5 impells the separating medium and additionallythe conveyor belt t impells the medium so that in the flowing arcuatestream between the discharge end of the trough i and the guide roller itthe action of the belt imparts increased velocity to the layer of mediumfurthest removed from the center of the roller 5 and closest the surfaceof the belt.

In connection with separation effected by the I aforedes'cribeclapparatus, the relative movement downward from each strata tothat belowrenowing the angle of reposa fluidiaes the sand-ymediurn; I

In connection withthearrangement shown in Figure 2 the apparatusembodiedtherein con stitutes a kinematic inversion of the relationshipshown inFigure 1. In Figure 2 the conveyor trough I2 is again acoveredtrough andslopes upwardly toward its 'dischargeend at an anglegreater than' the angle of repose ofthe separat ingmedium. At the lowerend ofthe trough, that is at that portion-preceding the rectilinearsection, there is provided an a-rcuate platel3 which in effectconstitutes a feed hopper; This arcuate plate is spaced above the bottomI4 Ofllh trough which is similarly arcuateatitsiower end and between theplate and the bottom of the trough and upwa-rdly along thetroughmovesthe conveyor I 5; 'Iliecdnveyor passes over spaced rollers IB'and II;the roller I I being at the bottom of the trough; Separating media:isied through inlet funnels I8 and I9 and the material to beseparated isintroducedthrough a duct: 20 disposed between thefunnels. Thisfeedhopper relationship including the funnels, duct and the arcuateplateis such that the separating media aresupplied at difierent ratesofintensity"to the rectilinearsefction of the trough in which sectionseparation is effected. A .conveyorbelt I5 maybe composed of segmentstravelling along the bottom of the trough and this belt advances'theseparating media containing the substance to be separated. If desiredthe belt may "be eliminated and the material may be advanced upthetrough by f orcefeeding utilizing suitable pumps in conjunction with thefunnels I8, I9 and the inlet duct 210. As indicated in thedrawing thebelt after passing over the upper pulley IE on its return run passesover pulley I I whose perimeteris above the arcuate portion of thebottomI4 and belt enters thefeed hopper or arcuate portion between the plateI3 and bottom I4. The movement of the beltadvances the lower layer ofthe separating medium in the trough at a higher velocity than the upperlayer thus" creating lrela tive movements betweenadjacent layers andproducing the same separating eifect as is efiected in the precedingarrangement with the result that the lightweight particlesare carried tothe top of the trough thereby effecting desiredseparation. After thestrata of medium and the materials entrained therein pass over upperpulley IBthe stream is divided into partial streams by one or moreadjustable blades 12I and from which partial streams the differentfractions of the substances to be separated are recovered byindividually screening these partial streams. a

The arrangement of Figure Zis of particular importance with regard tothe classification of substances composed oflarge size granulations suchas bulk coal Generally speaking, bulk coal is classified by methodsincluding hand picking which involve high costs and great loss of timewhen cons ide ring the output factor; With the present invention asdisclosed in Figure 2; including the upwardly sloping trough, the'structural relationship is provided1which permits housing the entireplant in a rather 'low volume of space since there is sufiicientvertical difference between the front feed and the upper dischargeend topermit of installation of screens and other complementary equipmentoperable onthe'material forseparating media andreturnin'g thesame to thefeed hopper. Withthis differencein elevation" suchequipmentcanbeinstalled in a suhstantially horizontal position. Themeans for returning the media to the troughs ihcludes a hopper or bin 29which receives media after it 'has passed through screen S. Thedischarge from-this hopper isdeposited on'aconveyorbelt whichdeliversthe media to another conveyor such as a bu'cketelevator 31. Thiselevator feeds the media toa conveyor 32 which is provided with blades,not shown,

to 'di'vertthe mediafro'm the conveyor belt to fall into the'funnelsIfland I9.- Atrough 33 feeds the substance to be separ'atedinto the ducts20.

In view of this lows'pac'eiactor and the fact that the process involvedis a dry process that is very simple to operate, the presentinvention-is particularly suitable for underground installation. Inother words the apparatus of Figure 2 can be installed rightin the minein connection with the grading of coal thereby providing an trated inFigure 3 in which cleaning devices in clude receptacles whichreceive thefractions of the substances being separatedfrom the partial streams. Inother wordsthe blade-22 divides the discharge into partial streamswhichflow over suitable screens denoted at S andthe fractions of material tobe separated pass ofi of these screens into "suitable troughs or hoppersH for conveyance to their final destinations The granulatedmedium thatpassesthrough j the screen S contains the residue and secondarygranulations and this granulated medium is discharged into a-bin orhopper 23 from whieh it passes to a conveyor belt which carries it toasuitable elevator such as abucket elevator 25 which carries it toanother conveyor 26 arranged over the funnels'2 and 3. The conveyor thatis above the feed funnels is providedwith suitable scrapers, notfshown,which divert medium into the respective hoppers and further diverta'partial stream PS into a decantation machine 27 which removes residueand secondary granulations from the 1 separating medium. The cleanseparating medium CS M passes through a drying drum 28 after itleavesthe decantation machine and is returned to the conveyorbeltj2Aearrying the screened medium from adjacent thedischargeend of thetrough. The justprevibusly described arrangement cleans only a partialstream of the medium. However it -"is obvious that the entire stream ofseparating medium passing through the screen at thedischarge endoffthetrough may pass directly to thedecantation machine thence throughthe drum and thence to a conveyor belt "arranged above the feed hoppersfrom which it is diverted into the respective hoppers. Obviouslyinsteadof a wet process theseparatingmedium from ad- .jacentthe discharge endcanbecleanedby air current.

It is therefore clear that l have provided a process and apparatus-forseparating in a specific gravity classification of bullc substancesutilizing finely granulated separating medium advancing in an inclinedtroueh'the f ed of the m t r through the trou h. being such that thevelocity of different layers of media in the trough is different and thestream flowing in a straight line through the trough is diverted to anarcuate fiow tangentially to the base of the trough in which differentstrata of the stream have different relative velocities.

What. I claim is:

l. A dry process for separating solid material in accordance with theirspecific gravities in a continuously moving stream of finely divided dryseparating media including feeding the material to be separated and themedia at one end of a zone disposed at. an angle sloping downwardly atleast slightly greater than the natural angle of repose, changing themovement of said stream from a straight line flow to an arcuate flowtans ntially to the straight line of fiow, thereby imparting differentrelative velocities to the strata, separating the strata in accordancewith the velocity thereof and removing the separated materials from therespective; strata. I

2. Aprocess as described in claim 1 in which the stream is confinedduring its change of movement and the. areuatefiow is of sufficientextent to divert the stream back toward its point of feed anddischarging the stream in an arcuate flow prior to separation of thestrata.

3. A dry process for separating solid materials in accordance with theirspecific gravities in a continuously moving stream of finely divided dryseparating media including feeding materials to be separated and themedia to one end of a separating zone, confining the material and mediainto a flowing stream of sufficient length and depth and at an anglegreater than the natural angle of slope of the media permitting relativevertical components of movement in the strata in the streain following.the angle of repose of the media to provide a fiuidizing flow, impartingan arcuate movement to the stream in a tangential direction with respectto the straight line fiow while simultaneously imparting increasedvelocity to one strata so that the strata with the materials to beseparated entrained therein move at different relative. velocities,discharging the strata while moving at different relative velocities,separating the strata into partial streams each con taining material ofdifferent specific gravities and separating the material from thepartial stream.

i. The process as defined in and by claim 3 in which the straight lineflow is directed downwardly and the increased velocity is imparted tothe upper strata.

5. The process as defined in and by claim 3 in which the major componentof straight line fiow is directed upwardly and the increased velocity isimparted to the lower strata.

6. The process as defined in and by claim 3 and including the return ofseparating media and reintroducing thereof into the feed end of thezone.

'7. An apparatus for dry media separation of solid materials inaccordance with their specific gravities including a trough disposed atan angle at least slightly greater than the natural angle of repose ofthe media and materials, vertically extending and longitudinally alignedfeeding means at the upper end of the trough including means for feedinga mass of finely granulated separating medium to form a lower stratum,means for feeding finely granulated separating medium to form'an upperstratum and means for feeding the materials to be separated interme'diate said strata, the relative movement downward from each strata tothat below following the angle of repose fiuidizing the medium toentrain particles of material of different specific gravity in thediiierent strata of medium, a member having a surface supported formovement in an arcuate path tangentially to the bottom, of the trough sothat the member receives strata from the trough and impells the same inan arouate path imparting greater velocity to at least one strata, saidstrata discharging with difierent relative velocities, and means forseparating the strata into partial streams in accordance with theirspecific gravities.

8. An apparatus as defined in and by claim '7 in which the trough slopesdownwardly and the member imparts increased velocity to the upperstrata.

9. An apparatus as defined in and by claim 7 in which the trough furtherincludes a major portion being inclined upwardly at an angle greaterthan the natural angle of repose, said member comprises aconveyor belt,the trough includes a downwardly sloping portion preceding the upwardlysloping portion, and means supporting and guiding the conveyor belt sothat a portion thereof follows an arcuate path disposed tangentiallywith respect to the bottom of both said trough portions, said beltmoving through out said upwardly sloping trough portion to impartgreater relative velocities to the strata flowing upwardly with thelowermost strata having higher velocity.

10. In an apparatus for separating materials according to specificgravities, the combination of an inclined trough having upper and lowerends, said trough confining a flowing stream of finely granulatedstratified separating medium and material to be separated therein andsaid trough being at least slightly more inclined than the natural angleof repose of said medium so that the mass of medium and materials flowsdownwardly, means at the upper end of the trough for feeding thematerials to be separated and the medium to the trough, rotatableconveying means at the lower end of the trough rotating in suchdirection as to continue the fiow of said stream in an arcuate path,said conveying means receiving and carrying strata of said stream atdifferent velocities corresponding to the radius of the circle they haveto follow, said conveying means comprising a roller so disposed that thebottom of the trough is tangent thereto, disc means at the sides of saidroller confining the how, and a moving belt transverse to and adjacentsaid disc means and following an arcuate path receiving and conveyingthe medium therein around the roller axis.

11. In an apparatus for separating materials according to their specificgravities, a combination of certain means including separatelongitudinally aligned channels including a central channel to receiveand feed materials to be separated and additional channels adjacentthereto respectively receiving masses of finely granulated separatingmedia, an inclined trough extending downwardly from said channels at anangle greater than the natural angle of repose of the media so that thematerials and media flow therethrough superimposed strata, said troughincluding an arcuate portion disposed tangentially with respect to thebottom thereof changing the direction or" flow of the strata, saidarcuate portion terminating in an upward inclination re ter han theangle of slope and said trough continuing said upward flow a substantialdis? 9 tance, means for conveying the strata through said upwardlysloping portion and for imparting increased velocity to the lowermoststrata, and means for discharging the strata at the upper end of theupwardly sloping portion in partial streams in accordance with theirspecific gravities and means for removing the media from said streams.

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